1. Field of the Invention
The present invention relates to a parking sensor apparatus and method to keep air brakes from interfering with the parking sensor apparatus and especially to a technique that prevents noise of an air brake from interfering with detecting obstacles and determining a distance to the obstacle to allow the parking sensor apparatus to be used on vehicles with air brakes.
2. Description of Related Art
Parking sensor apparatus detect an obstacle and determine a distance from the sensor to the obstacle with ultrasonic sound when backing a vehicle. The parking sensor apparatus operates on principles similar to radar but operates at ultrasonic frequencies rather than radio frequencies and comprises a controller, an ultrasonic transducer and alarm. The ultrasonic transducer transforms an electronic signal to an ultrasonic pulse, transmits the ultrasonic pulse, receives an ultrasonic echo and transforms the ultrasonic echo to an electronic signal.
With reference to FIG. 4, the ultrasonic transducer responds to a signal from the controller and a reflected echo (B) from an obstacle. With reference to FIG. 5, any reflected echo will be buried in noise generated by the release of air from air brakes on a vehicle such as a truck or bus. Noise from the air brake causes the ultrasonic transducer to saturate and generate an electronic signal indicating receipt of a high amplitude signal. Consequently, the controller activates the alarm in a false alarm situation. Any significant number of false alarms will cause a driver to lose confidence in the parking sensor apparatus. Therefore, the conventional parking sensor apparatus cannot filter or block air brake interference and produces false alarms.
Consequently, conventional parking sensor apparatus cannot be used in vehicles with air brakes. The situation can be mitigated significantly to allow a parking sensor apparatus to be used on vehicles with air brakes.